1. Field of the Invention
The present invention relates to a wavemeter for measuring a wavelength of an optical signal (a light signal) multiplexed in a WDM (wavelength division multiplexing) technique or the like.
2. Description of the Related Art
In recent years, the information communications technology which is represented by Internet, portable telephones or the like has been developed remarkably. In proportion to the development of the technology, an amount of information which is transmitted through a transmission path for a predetermined time, increases rapidly. One of the most important transmission paths supporting the information communications technology is an optical fiber. A number of optical fibers have already been provided under the ground, on the bottom of the sea or the like. The optical fibers have been used actually.
In order to rapidly increase communication traffic capacity, new optical fibers are provided. Further, a system for transmitting a large amount of information at a high speed by using the existing optical fibers is desirable. One of the above systems is a WDM technique.
The WDM technique is one for using one optical fiber in multiple by utilizing the characteristic that lights having different wavelengths do not interfere with each other and by transmitting a plurality of optical signals having different wavelengths synchronically.
In the system using an optical signal having a single wavelength according to an earlier development, the data transfer rate is limited to 2.5 to 10 bps. In the WDM technique, a transfer capacity of several terabit per second can be realized, for example, by multiplexing one hundred twenty-eight 10-Gbps signals.
In order to realize the transmission using the WDM technique (hereinafter, referred to as xe2x80x9cWDM transmissionxe2x80x9d), an apparatus for precisely evaluating a transmission property during the WDM transmission is required. As such an apparatus, a wavemeter for measuring and analyzing a spectrum of a plurality of optical signals has been developed.
In such a wavemeter, a function for monitoring a transition of a variation in a wavelength of an optical signal in a communication state during the WDM transmission, could not be realized.
When a wavelength of an optical signal or the like is varied beyond the range of the performance of the wavemeter in the WDM transmission, a quality of a signal remarkably deteriorates at a receiving part. Therefore, it is necessary that in the WDM transmission in which a plurality of optical signals are multiplexed, each multiplexed optical signal is monitored.
In order to solve the above-described problems, an object of the present invention is to monitor a transition of a variation in each optical signal multiplexed in the WDM transmission or the like and is to monitor a communication state during the WDM transmission.
That is, in accordance with one aspect of the present invention, a wavemeter for measuring a signal light which is obtained by multiplexing a plurality of optical signals in a predetermined system and which is transmitted, comprises:
a reference setting unit (for example, a CPU 6 shown in FIG. 1; Step S2 shown in FIG. 5) for setting a reference value for measurement of the signal light obtained by the predetermined system,
a measuring unit (for example, a CPU 6 shown in FIG. 1; Step S3 shown in FIG. 5) for continuously measuring the transmitted signal light,
a specifying unit (for example, a CPU 6 shown in FIG. 1; Step S3 shown in FIG. 5) for specifying each optical signal multiplexed into the signal light, in accordance with a result of a measurement carried out by the measuring unit,
a variation measuring unit (for example, a CPU 6 shown in FIG. 1; Step S4 shown in FIG. 5) for calculating a variation in a physical value of each optical signal specified by the specifying unit in accordance with the reference value for measurement, and
an output unit (for example, a CPU 6 shown in FIG. 1; Steps S6 and S7 shown in FIG. 5) for outputting a transition of the variation calculated by the variation measuring unit.
The variation calculated by the variation measuring unit may be a difference between an electric energy of each optical signal specified by the specifying unit and the reference value for measurement, which is set by the reference setting unit.
The variation calculated by the variation measuring unit may be a difference between a wavelength of each optical signal specified by the specifying unit and the reference value for measurement, which is set by the reference setting unit.
According to the present invention, because a variation of each measured optical signal, for example, a variation in an electric energy, that in a wavelength or the like, is calculated to output a transition thereof, it is possible to monitor the transition of the variation in a transmission status of a multiplexed signal light. Therefore, a temperature property of a light source, for example, used in the WDM transmission can be monitored.
The wavemeter may further comprise a setting unit (for example, a CPU 6 shown in FIG. 1; Step S1 shown in FIG. 5) for setting number of times of measurement of the signal light,
wherein the transmitted signal light is continuously measured the number of times, which is set by the setting unit.
When the number of times of measurement of the signal light is set by the setting member, the measuring unit continuously measures the transmitted signal light the number of times, which is set by the setting unit. Therefore, the number of times of measurement can be set freely and the multiplexed signal light can be measured and monitored more freely.
The plurality of optical signals may be multiplexed by using a WDM technique.
It is possible to realize the wavemeter which can be applied to the WDM transmission which is used as a multiplexing method for an optical signal.
In accordance with another aspect of the present invention, a wavemeter comprises:
a reference setting unit for setting a reference physical value of each optical signal of a reference multiplexed light,
an optical signal specifying unit for specifying each optical signal of a multiplexed light to be measured,
a variation measuring unit for calculating a variation between the reference physical value of each optical signal of the reference multiplexed light, and a physical value of each optical signal of the multiplexed light to be measured, and
an output unit for outputting the variation.